Sensitive diaphragm for light pressure



May 31, 1927. 1,630,292

J. ELY

SENSITIVE DIAPHRAGM FOR LIGHT PRESSURE Filed July-22 1926 INVENTOR A ATTORNEY,

- accurate response to the Tatented May 31, 1927.

' @NETE stares JAMES ELY, OF'ROOHESTER, NEW YORK, ASSIGNOB TO TAYLOR INSTRUMENT COM- PANIES, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

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Application filed July 22,-

This invention relates to an improvement in" apparatus for measuring and recordmg pulsating pressures and more 1n particular to an improvement in apparatus of the type disclosed. in the patent to Levin No. 1,532,705. I r

In instruments for recording small pulsating pressure variations or, more in particular, for translating pulsating pressure reactions of the blood upon the constricting cuif mechanism to a recording mechanism, a pressure-responsive element of high sensitivity must beprovided. A

Of all the pressure-responsive devices available for similar purposes, the resilientdiaphragm construction is best adapted for carrying out the particular object. However, only comparativelyv few materials have been found suitable to satisfy the practical requirements. Of all the materials experrmented with, such as for instance admiralty nickel metal, aluminum, steel, brass, bronze,- oiled silk, bakelite varnish on thin 'paper, parchment celluloid gave the best results.

However it was found that under some conditions the celluloid diaphragm was subject to variations of sensitiveness and response and in some instances became even inoperative for the purposes of the invention, due to absorption of moisture from .the air. While celluloid is not highly hygroscopic, the action of moisture upon. the diaphragm may affect its physical and mechanical characterist'fcs de nded upon for uid. pressure imulses, to such an extent as to materially impair its utility for the articular purpose. Various remedies have een tried but have failed to give the desired efi'ect without impeding the mechanical qualities of the diaphragm. v

The object of the invention is a means for protecting sensitive diaphragms of the char- ,acter involved without material impairmentof the mechanical properties thereof depended upon for sensitive response to variations of Ipressure. have found that thin sheets of alumtanned colon leather placed loosely on one or both sides of the diaphragm afltords a shield-1 or screen against the action of moisture and at the same time do not materially interfere with the normal intended function of the diaphragm. r

In the drawing, which forms a part of the 1926. Serial Na-124,245.

specification, the invention is illustrated as,

forming, part of a diaphragm construction for use in connection with a recording sphygmomanometer such as disclosed in the ing a central sectional viewthrough the dia-.

phragm. I

The diaphragm construction herein shown consists of a rigid housing composed of two complementary halves 1 and 2 having flanges 1 and 2 bolted together and holding be-' tween them in clamped relation, as is usual, the diaphragm 3. The nipples 4 and 5' are provlded for affording detachable pneumatic connections to the opposite sides ofthe diaphragm 3. The stem 6 projecting from the center of the diaphragm constitutes one of the elements for translating motion of, the diaphragm to indicating or recording mechanism which does not form'a part of the present invention.

The construction thus far described may considered as representing ordinary englneering practice and prior art so far as its relation to the invention proper is concerned.

f On opposite sides ofthe diaphragm are isposed sheets 7 and 8 of alum-tanned colon leather the thickness of which is of theorder of .0005. The sheets or disks are co-extensive with the diaphragm and are clamped at the eriphery between th flanges 1 and 2, pre erably together with gaskets-9 and 10 and at the center between washers 11 or the like held together by means of nuts 12 cooperating with the screw-threaded stem 6.

The disks 7 and 8 of colonleather are so dimensioned and'disposed that they overlie the diaphragm in a slack condition i. e. so that they can readily follow the movement of the diaphragm without exerting a pressure uponit'. It should be noted that the diaphragm is preferably disposed in'a vertical direction so that not even the weight of the leather, as negligible as it is, can have a material effect upon the action of the diaphragm.

The colon leather is so thin and so ext'remly flexible and pliable that under the pneumatic Jpressure actions transmitted to it or due to varying differences of pressure existing on opposite sides of the diaphragm, the disks 7 and 8 transmit the pressure 1mpulses or yield to pressura impulses Without' substantially modifying the motion of the diaphragm or in any Way superimposing upon the motion of the latter characteristics Which are not functions of the diaphragm proper; v I

While I have made special reference to a celluloid diaphragm and while celluloid is-\ .thin sheet of pliable material of the order of alum-tanned colon leather.

2. In a pressure-responsive device of the diaphragm. ty e, the combination of a diaphragm sensi ve to small changes in penumatic pressure and a shield against 1nflu-.

ences of moisture, said shield comprising a thin sheet of pliable material of the order of alum-tanned colon leather on each side of the diaphragm. j

'3. In pressure-responsive devices of the diaphragm type, the combination of a celluloid diaphragm having a thickness of about .0015 and a shield against influences of moisture comprising a sheet of alum-tanned colon leather having a thickness of about In testimony whereof I afiix my signature.

JAMES ELY. 

